A hearing-aid device and a method for transmitting sound through 
bone conduction are disclosed. The hearing-aid device comprises a piezoelectric-type 
actuator, housing and connector. The piezoelectric 
actuator is preferably a circular flextensional-type 
actuator mounted along its 
peripheral edge in a specifically designed circular structure of the housing. During operation, the bone-conduction 
transducer is placed against the mastoid area behind the ear of the patient. When the device is energized with an alternating electrical 
voltage, it flexes back and forth like a circular membrane sustained along its periphery and thus, vibrates as a consequence of the inverse piezoelectric effect. Due to the specific and unique designs proposed, these vibrations are directly transferred trough the 
human skin to the 
bone structure (the 
skull) and provide a means for the sound to be transmitted for patients with hearing malfunctions. The housing acts as a holder for the actuators, as a pre-stress application platform, and as a 
mass which tailors the 
frequency spectrum of the device. The apparatus exhibits a performance with a very flat response in the 
frequency spectrum 200 Hz to 10 kHz, which is a greater spectrum range than any other prior art devices disclosed for bone-conduction transduction which are typically limited to less than 4 kHz.